Method of making a thermoplastic-based article and a thermoplastic-based article made thereby

ABSTRACT

An article, such as a lens article ( 10, 10′, 10″, 100 ) containing a first component, e.g., a filter ( 14, 14 ′), or component thereof, having a minimum degradation temperature, and a second component, e.g., a substrate ( 22, 22 ′), comprising a blend of first and second thermoplastic polymers. The first polymer, which has a glass transition temperature higher than the minimum degradation temperature of the first component, is selected based upon its ability to provide the article with one or more desirable characteristics. The second polymer is blended with the first polymer in a predetermined amount that provides the blend with an adjusted glass transition temperature lower than the minimum degradation temperature of the first component so that the first and second components can be heat processed together at a temperature greater than or equal to the adjusted glass transition temperature but below the minimum degradation temperature.

RELATED APPLICATION DATA

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/331,062, filed Dec. 27, 2002 and titled,“Thermoformable Polarized Lens With Substrate Having Adjusted GlassTransition Temperature,” now U.S. Pat. No. 6,834,956, that isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of manufacturing.In particular, the present invention is directed to a method of making athermoplastic-based article and a thermoplastic-based article madethereby.

BACKGROUND OF THE INVENTION

Sometimes a material having one or more properties suited for use in aparticular article of manufacture cannot be used because that materialis not compatible with the process that is the most desirable for makingthe article. For example, in the context of polarized ophthalmic lenses,it is often desirable to attach a flexible polarizer to a rigidsubstrate to make a composite and then thermoform the composite toprovide the curvature(s) necessary for the type of lens, e.g., plano,powered, multi-focal, etc., for which the composite will be used. Afterthermoforming, the composite may then be finished, e.g., byappropriately shaping its periphery to suit the finished lens and/orapplying one or more optical coatings, such as a hardcoat, to thesurfaces of the composite. Alternatively, the thermoformed composite maybe used as pre-curved polarizing insert for a lens that, when finished,will include one or more additional optical layers attached to theinsert. The resulting multilayer lens may then be finished in a mannersimilar to the manner mentioned, e.g., by appropriately shaping theperiphery of the lens and/or applying one or more optical coatings tothe surfaces of the lens.

Conventional polarizers used in ophthalmic lenses are often a sandwichof three thermoplastic layers. The middle layer is the polarizing layer,which frequently comprises a polyvinyl alcohol (PVA) layer containingeither a hydrophilic dichroic dye or iodine that provides the polarizingproperty. The outer two layers are often made of the same material aseach other, typically a cellulose-based polymer, such as cellulose acetobutyrate (CAB). Such polarizers provide very good polarizingperformance, but they must not be heated to temperatures equal to orgreater than their “minimum degradation temperature,” i.e., thetemperature at which their performance/quality noticeably degrades dueto physical changes caused by the elevated temperature. If thesepolarizers are heated to their minimum degradation temperature orhigher, particularly for a sustained period, they will often becomeunsuitable for use because the degradation caused by the elevatedtemperature will reach or exceed an acceptable limit.

For example, a conventional CAB-PVA-CAB polarizer sandwich typically hasa minimum degradation temperature in a range of about 95° C. to about120° C., depending upon the particular formulation of the variouslayers. Relative to the CAB part of the polarizer, the amount and typeof degradation generally depends on time and the internal constituentsof the CAB. When such a polarizer is heated to or above its minimumdegradation temperature, the CAB degrades, typically by yellowing in thefirst instance, followed by the development of air bubbles and/orblisters and increased stiffness. Similar degradation also occurs withcellulosetriacetate (CTA) but at slightly higher temperatures. Otherdegradation may also occur, depending upon the makeup of the polarizer.For example, depending upon the adhesive used bond the CAB layers to thePVA layer, the bond may separate in places and cause blisters among thelayers. In another example wherein iodine is the polarizing substanceincorporated into the PVA, the iodine's ability to provide a polarizingeffect begins to irreversibly degrade at a temperature of about 100° C.(the minimum degradation temperature) by changing color. Moistureaffects the amount and speed of the degradation; the higher the moisturecontent, the greater and faster is the degradation. Starting around 120°C., the polarizer begins to fade and lose polarizing efficiency.

Unfortunately, some of the most desirable thermoplastics for thesubstrate, based on their optical and durability properties, e.g., purepolycarbonates and some pure methacrylates, e.g., poly (methylmethacrylate) (PMMA), have glass transition temperatures that are higherthan the minimum degradation temperatures of the polarizers. Forexample, a pure polycarbonate typically has a glass transitiontemperature in a range of about 135° C. to about 155° C., and a puremethacrylate typically has a glass transition temperature in a range ofabout 105° C. to about 110° C. Therefore, a manufacturing process thatincludes thermoforming the substrate and polarizer together with oneanother, which generally requires the substrate to be heated to itsglass transition temperature or higher, would not be suitable becausethis temperature is higher than the minimum degradation temperature ofthe polarizer. Consequently, the polarizer would degrade, likely to anunacceptable extent. It is noted that in a thermoforming process thatincludes heating the article to a temperature lower than the glasstransition temperature at issue and subjecting it to relatively largepressure is often not an acceptable alternative for ophthalmic lensesdue to the residual stresses that this process imparts into article.Besides, even the lower temperatures used in this alternative are oftenhigher than the minimum degradation temperature of the polarizer.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a method of makingan article. The method comprises the step of providing a first componenthaving a minimum degradation temperature. A second component is providedthat includes a polymer blend that contains a first polymer having afirst glass transition temperature higher than the minimum degradationtemperature. The polymer blend has a second glass transition temperatureadjusted downward from said first glass transition temperature. Thefirst component and second component are placed into working relationwith one another so as to form a composite. The composite is thermallyprocessed at a temperature below the minimum degradation temperature.

In another aspect, the present invention is directed to a method ofmaking an article that includes a first component and a second componentthermally processed in conjunction with the first component, the firstcomponent having a minimum degradation temperature and the secondcomponent having at least one desired characteristic. The methodcomprises selecting a first polymer for the second component based onthe ability of the first polymer to provide the at least one desirablecharacteristic, the first polymer having a glass transition temperaturehigher than the minimum degradation temperature. As second polymer isblended with the first polymer so as to adjust the glass transitiontemperature lower than the minimum degradation temperature so that thefirst and second components can be thermally processed at a temperaturelower than the minimum degradation temperature.

In a further aspect, the present invention is directed to an articlecomprising a first component having a minimum degradation temperature. Asecond component is located in working relation with the firstcomponent. The second component has at least one characteristic andcomprises a blend of a first polymer and a second polymer. The firstpolymer is selected based on its ability to provide the at least onecharacteristic and has a glass transition temperature greater than theminimum degradation temperature. The second polymer is selected toadjust the glass transition temperature to a temperature lower than theminimum degradation temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings illustrateforms of the invention that are presently preferred. However, it shouldbe understood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a perspective view of a thermoplastic-based article of thepresent invention;

FIG. 2 is a partial cross-sectional view of a mold assembly and thethermoplastic-based article of FIG. 1 taken along line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view of an alternativethermoplastic-based article of the present invention;

FIG. 4 is a partial cross-sectional view of a mold assembly and anotheralternative thermoplastic-based article of the present invention; and

FIG. 5 is a partial cross-sectional view of the mold assembly of FIG. 2and yet another alternative thermoplastic-based article of the presentinvention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description of various embodiments of theinvention, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is to be understood that otherembodiments may be utilized and that changes may be made withoutdeparting from the scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention may be determined from theappended claims.

Referring now to the drawings, in general the present invention isdirected to a method of making a thermoplastic-based article, such as,e.g., the ophthalmic lens article 10 shown in FIG. 1. Ophthalmic lens“article” 10 is referred to as such because it can be either a lens inand of itself or, alternatively, an insert for incorporating into afinished lens, e.g., as described below in connection with FIG. 4. Likeall thermoplastic articles, during manufacturing lens article 10 or aportion thereof is subjected to one or more elevated temperatures thatare generally significantly higher than the temperatures that thearticle will experience during its intended use. These elevatedtemperatures may be due to any one or more of the following: molding,thermoforming, extrusion and annealing, among others.

As noted in the Background section above, certain thermoplastics haveproperties that are well-suited to a particular application. Forexample, in the context of lens article 10, it is known thatpolycarbonate is well-suited for ophthalmic lenses due to variousdesirable characteristics, such as its optical clarity, hardness,toughness and relatively high index of refraction. However, whilepolycarbonate may be desirable for reasons relating to its optical anddurability characteristics, certain properties of polycarbonate, such asits glass-transition temperature, can increase the difficulty ofincorporating various desirable features into lens article 10.

For example, as illustrated in FIG. 2, it may be desirable to providelens article 10 with a filter 14 comprising a filtering layer 18 placedin working relation with a substrate 22 in any suitable manner known inthe art. Filtering layer 18 may be provided with at least one of apolarizing function or a photochromic function, among others. In thecontext of polarizing, filter layer 18 may comprise a suitablethermoplastic, such as a polyvinyl alcohol (PVA), e.g., polyvinylene, orpolyacetelyne, containing iodine or a dichroic substance, such asChloratine Fas Red, Chrysophenine, Sirius Yellow, Bensopurpurine, DirectFast Red, Brilliant Blue 6B, Chlorasol Black BH, Direct Blue 2B, DirectSky Blue, Diamine Green, Congo Red and Acid Black, among others, ormixtures thereof, that provides this layer with a polarizing ability.Filter layer 18 may be sandwiched between two protective layers 26 madeof, e.g., a cellulosic material, such as cellulose aceto butyrate (CAB),among others, so as to form a standalone filter laminate. Generally,filter 14 is attached to substrate 22, which generally provides arelatively robust structure for supporting the filter, which istypically relatively thin and flexible, as those skilled in the art willappreciate. When filter 14 is a photochromic filter, a suitablephotochromic substance, such as naphthopyrans, spironapthopyrans,fulgides, fulgimides, salicylates, triazoles, oxazoles, azobenzenes andsilver halide, among others, may be incorporated into filtering layer18, which may also include a material, e.g., CAB, polypropylene,poly(vinyl chloride) and poly(vinyl acetate), among others, suitable forcontaining or supporting the selected substance. Such a photochromicfiltering layer 18 may be attached to substrate 22 directly or,optionally, first sandwiched between protective layers 26, if necessary,before being attached to the substrate by appropriate means, such asadhesive bonding.

In one method of manufacturing lens article 10, substrate 22 is providedin flat sheet or flat plate form, and filter 14 is attached to the flatsubstrate to form the article prior to providing the article with itsdesired contour(s), such as curvature(s) or stepped multi-focalcontour(s), e.g., by thermoforming. (It is noted that the convex side 30and the concave side 32 may be provided with the same or differentcurvature as required to achieve a particular result. It is also notedthat it may be desirable to anneal lens article 10 after thermoformingin order to relieve residual stresses in the article.) As discussed inthe Background section above, it is well-known that iodine-basedpolarizers, such as a polarizing version of filter 14, can be damaged byexposure to elevated temperatures. For example, the iodine in aPVA/iodine polarizer generally begins to deteriorate at a temperature(i.e., the minimum degradation temperature) in a range of about 95° C.to about 120° C., thereby degrading or destroying the polarizer'spolarizing ability.

Higher temperatures can also be detrimental to protective layers 26. Forexample, the CAB layers of a CAB/PVA/CAB polarizer generally begin todegrade at a temperature in a range of about 95° C. to about 120° C.,typically by yellowing in the first instance, thereby rendering thepolarizer unsuitable. In addition, depending on the adhesive (not shown)used to bond the protective layers 26 to filter layer 18 and/or filter14 to substrate 22, elevated temperatures can cause the protectivelayers and/or filter to blister. Such blistering would render lensarticle 10 unacceptable for its intended purpose.

Polycarbonates, e.g., those sold under the trademarks LEXAN® andMAKROLON® by General Electric Corporation and Bayer Corporation,respectively, generally have a glass-transition temperature in a rangeof about 135° C. to about 155° C. Consequently, if substrate 22 weremade of one of these polycarbonates, it would generally be necessary toraise the temperature of the substrate and filter 14 to at least theglass transition temperature of that polycarbonate, i.e., about 135° C.or higher, in order to thermoform and/or anneal lens article 10.However, heating filter 14 to such a temperature would exceed itsminimum degradation temperature. Therefore, despite polycarbonate beinga highly desirable material from optical and durability viewpoints, itis generally not desirable from a manufacturability viewpoint.

Although a pure polycarbonate would generally not be suitable for use assubstrate 22 in the manufacturing process described above due to thedeterioration of filter 14 caused during thermoforming and/or annealing,the pure polycarbonate (i.e., the first polymer) may be blended, orcopolymerized, with a second polymer other than polycarbonate, e.g.,polyethylene teraphthalate, so as to essentially reduce the glasstransition temperature of the polycarbonate to an adjusted glasstransition temperature that will allow lens article 10 to bethermoformed and/or annealed at a temperature lower than the minimumdegradation temperature of filter 14. This concept may be readilyextended not only to carbonates other than polycarbonate (see below),but also to other polymers generally. Those skilled in the art willreadily understand how to apply the basic concepts of the presentinvention to myriad polymers based on the particular thermoplastic-basedarticle being considered and the characteristics that are desirable forthe component of that article at issue. Consequently, it is notnecessary to provide an exhaustive list of all permutations of polymerblends. However, a few examples are provided herein for a more robustdisclosure. It is noted that the second polymer blended with the firstpolymer that provides the desirable characteristics is typically, butnot necessarily, not from the same group as the first polymer. Forexample, if the first polymer is a carbonate, the second polymer istypically, but again not necessarily, not a carbonate.

Other examples of carbonate blends having glass-transition temperatureslower than pure polycarbonate and lower than the temperature at whichfilter 14 would start to degrade include certain ones of the blends madeof aliphatic polyester-carbonates incorporating “diaryl carbonates”disclosed in U.S. Pat. No. 5,654,380 (e.g., the carbonate blenddisclosed in Example 1 has a glass-transition temperature of 104° C.)and the blend disclosed in U.S. Pat. No. 5,410,014, which discloses acopolymer of aromatic-aliphatic polycarbonate having a glass transitiontemperature of about 119° C. Each of U.S. Pat. Nos. 5,654,380 and5,410,014 are incorporated herein by reference in their entireties.

In one particular embodiment, substrate 22 may comprise a blend of 70parts of polycarbonate to 30 parts of polyethylene teraplithalate thathas an adjusted glass transition temperature of about 121° C. This blendis commercially available under the trademark XYLEX® from the GeneralElectric Company. It has been observed that sheets of this blend can bethermoformed at temperatures between about 120° C. and about 140° C.Clearly, at the upper end of this range this particular blend is notsuitable for use with an iodine/PVA-based polarizer, which has a minimumdegradation temperature in a range of about 95° C. to about 120° C.based on the presence of iodine. However, the lower end of the range maybe suitable for such a polarizing layer. That said, experimentsperformed to date have shown that thermoforming at the lower end of therange can be non-uniform.

In another embodiment in which substrate 22 comprises a 50 parts to 50parts blend of polycarbonate and polyethylene teraphthalate (alsoavailable from General Electric under the trademark XYLEX®) having anadjusted glass transition temperature of about 87° C., it has beenobserved that sheets of this blend can be readily thermoformed at about95° C. Referring to FIG. 2, the curvatures of sides 30, 32 of lensarticle 10 thermoformed at 95° C. using the thermoforming assembly 36 ofFIG. 2 matched, respectively, the curvatures of surfaces 40, 42 of thethermoforming assembly. This relatively low thermoforming temperature issuitable for avoiding degradation of the iodine/PVA-based polarizerdiscussed in the preceding paragraph.

If lens article 10 is to be a lens, as opposed to an insert, one or moreoptical coatings, such as hardcoat layers 46, may be provided to thearticle on each of sides 30, 32. This would typically be done after lensarticle 10 has been thermoformed.

In addition, or alternatively, to one or more dichroic dyes beingincorporated into filter 14, one or more dichroic dyes may beincorporated directly into substrate 22. Indeed, in alternativeembodiments of article 10 having photochromic properties withoutpolarizing properties, filter need not be provided. In this case, thephotochromic dye(s) could be incorporated only in substrate. In thisconnection, some photochromic dyes have been reported to not performwell in polymers with high glass transition temperatures and performbetter in polymers with lower glass transition temperatures. Somephotochromic dyes have two geometrical forms, e.g., one form “open” andthe other form “closed,” and the photochromic action is accompanied byopening and closing the molecule. In a matrix having a low glasstransition temperature, the matrix has greater mobility and thephotochromic molecule can change forms more readily. Consequently,substrate 22 in this scenario could be a polymer blend having a glasstransition temperature adjusted in the manner described above inconnection with the embodiment incorporating filter. In this case, theglass transition temperature of substrate 22 may be adjusted prior toadding any photochromic dyes thereto. Suitable polymer blends forsupporting direct addition of one or more photochromic dyes may includeany of the exemplary blends discussed above, including themethacrylate/butyldyene blend and the polycarbonate/polyethyleneteraphthalate blend, among others.

FIG. 3 shows an alternative lens article 10′ of the present inventionthat may also be used as a filtering lens or a filtering insert inmanner similar to the manner described above relative to lens article ofFIGS. 1 and 2. Rather than having a single blended-polymer substrate 22to which filter 14 is attached as with lens article 10 of FIG. 2, lensarticle 10′ of FIG. 3 includes two blended-polymer layers 22′ attachedto opposite sides of a filter 14′. Similar to lens article 10′ of FIGS.1 and 2, lens article 10′ of FIG. 3 would typically be assembled withsubstrates 22′ in flat-plate form, such that the entire article,including filter 14′, would need to be thermoformed in order achieve thecontours shown in FIG. 3. Filter 14′ may be any filter suitable for lensarticle 10′, such as the polarizer-type or photochromic filter 14 shownand described above relative to FIG. 2.

Like substrate 22 of FIG. 2, each substrates 22′ of FIG. 3 may contain apolymer blend that includes a first polymer selected primarily for itsability to provide lens article 10′ with one or more desirablecharacteristics as discussed above. Also similar to the discussionabove, each substrate 22′ further includes a second polymer blended withthe first polymer in a predetermined amount so as to essentially lowerthe glass transition temperature of the first polymer so that lensarticle 10′ can be thermally processed, e.g., thermoformed and/orannealed, at a temperature that will not unacceptably degrade filter14′, or any of its components.

FIGS. 4 illustrates lens article 10 of FIGS. 1 and 2 being used as afiltering insert for an ophthalmic lens 100. In one embodiment, lens 100is made by placing article 10 between mold parts 104 of an injectionmolding or injection/coining machine (not shown) and injecting orinjecting/coining a high-impact polymer layer 108 against the concaveside of the article. In an alternative embodiment, high-impact polymerlayer 108 may be formed on the convex side of lens article 10. However,it appears that a greater impact strength can be achieved by forminglayer 108 on the concave side.

A suitable method of forming high-impact polymer layer 108 is theinjection/coining process disclosed in detail in U.S. Pat. No. 6,270,698to Pope, which is incorporated by reference herein in its entirety.High-impact polymer layer 108 may be made of any suitable polymer orpolymer blend, including a polymer blend, including thepolycarbonate/polyethylene teraphthalate blend ormethacrylate/butyldyene blend described above, that is made inaccordance with the present invention, i.e., generally, by firstselecting a first polymer based on its ability to provide one or moredesirable characteristics and then blending the first polymer with asecond polymer so as to create a blend having both good characteristicsand a glass transition temperature lower than the glass transitiontemperature of the polymer originally selected for its ability toprovide the desirable characteristic(s). During the injection/coiningprocess, high-impact polymer layer is molded at a suitable moldingtemperature, which is generally between about 415° F. and about 480° F.for polycarbonate copolymers and about 400° F. for the acryliccopolymer.

Using the injection/coining process of the Pope patent, using apolycarbonate/polyethylene teraphthalate blend for each of substrate 22and high-impact polymer layer 108 and using iodine/PVA for filteringlayer 18, it was seen that the high-impact polymer layer bonded verywell to the substrate and filtering layer did not degrade. In addition,use of this process resulted in minimal residual stress in layer 108. Ina particular specimen of lens 100 made using the Pope process with thematerials just cited, the overall thickness of the lens wasapproximately 2. mm. This specimen passed the tests set forth in theAmerican National Standards Institute (ANSI) Z78 Standard for Eye andFace Protection. Specimens of lens 100 thinner than 2.4 mm can also passthese tests, depending upon the materials selected for the variouslayers of the lens and the level of residual internal stresses remainingin the lens after its manufacture.

FIG. 5 shows a lens article 10″ that is similar to lens article 10 ofFIG. 2, except that substrate 22 is located on the convex side 30 of thearticle rather than the concave side 32, as shown in FIG. 2. This may beachieved, e.g., simply by flipping the flat filter 14/substrate 22precursor to article 10 side 30 for side 32 in thermoforming assembly 36relative to FIG. 2 prior to thermoforming. All other aspects of article10″ may be the same as described above relative to lens article 10.

The following six examples outline results obtained from differentexperiments to form example embodiments of article 10 of the presentinvention. The experiments were carried out to determine the properprocess and structure for articles suitable for use as stand-alonepolarized lenses, or as inserts for injection-molded polarized lenses.

EXAMPLE 1

An iodine-based polarizer having transmittance for visible light of 37%was bonded between two layers of cellulose acetobutyrate, then bonded toone sheet (substrate) of 0.5 mm thick LEXAN polycarbonate to form thecomposite structure. Rectangles approximately 60 mm by 70 mm were cutfrom the composite structure. The composite rectangles were placed in aconventional vacuum thermoformer with spherical cups having a radius of90 mm. The composite rectangles were heated in the thermoformer to 95°C. for 8 minutes. The curvature of the composite rectangles was veryirregular and minimal. However the iodine-based polarizer did not showany degradation during the process. Similar results were obtained whenthe LEXAN polycarbonate sheets were replaced with sheets ofpolycarbonate from the Mobay Corp.

EXAMPLE 2

An iodine-based polarizer having transmittance for visible light of 37%was bonded between two layers of cellulose acetobutyrate, then bonded toone sheet (substrate) of 0.5 mm thick LEXAN polycarbonate to form acomposite structure. Rectangles approximately 60 mm by 70 mm were cutfrom the composite structure. The composite rectangles were placed in aconventional vacuum thermoformer with spherical cups having a radius of90 mm. The composite rectangles were heated in the thermoformer to 140°C. for 8 minutes. The composite rectangles had an irregular curvaturethat was less than the mold surface curvature. The iodine polarizer wasdegraded and the cellulose acetobutyrate layers were yellowed andblistered. Similar results were obtained when the sheets of LEXANpolycarbonate were replaced with sheets of polycarbonate from the MobayCorp.

EXAMPLE 3

Rectangles approximately 60 mm by 70 mm were cut from a sheet(substrate) of 0.5 mm thick blend of 70/30 polycarbonate/polyethyleneteraphthalate (XYLEX). The rectangles were placed in a conventionalvacuum thermoformer with spherical cups having a radius of 90 mm. Therectangles were heated in the thermoformer to 120° C. for 8 minutes. Theresultant curvature of the rectangles was irregular. Further, thepolarizer showed slight degradation and the cellulose acetobutyrateshowed slight yellowing.

EXAMPLE 4

An iodine-based polarizer having transmittance for visible light of 37%was bonded between two layers of cellulose acetobutyrate, then bonded toone sheet (substrate) of 0.5 mm thick blend of 70/30polycarbonate/polyethylene teraphthalate (XYLEX). Rectanglesapproximately 60 mm by 70 mm were cut from the composite structure. Thecomposite rectangles were placed in a conventional vacuum thermoformerwith spherical cups having a radius of 90 mm. The composite rectangleswere heated in the thermoformer to 120° C. for 8 minutes. The resultantcurvature of the rectangles was irregular. Further, the polarizer showedslight degradation and the cellulose acetobutyrate showed slightyellowing.

EXAMPLE 5

An iodine-based polarizer having transmittance for visible light of 37%was bonded between two layers of cellulose acetobutyrate, then bonded toone sheet (substrate) of 0.5 mm thick blend of 50/50polycarbonate/polyethylene teraphthalate (XYLEX). Rectanglesapproximately 60 mm by 70 mm were cut from the composite structure. Thecomposite rectangles were placed in a conventional vacuum thermoformerwith spherical cups having a radius of 90 mm. The composite rectangleswere heated in the thermoformer to 100° C. for 8 minutes. The resultantcurvature of the composite rectangles was regular and closely matchedthe curvature of the mold surface. Further, the iodine polarizer showedno degradation and the cellulose acetobutyrate layers did not yellow orblister. This article can be used as a stand-alone polarizing lens.

EXAMPLE 6

An iodine-based polarizer having transmittance for visible light of 37%was bonded between two layers of cellulose acetobutyrate, then bonded toone layer (substrate) of 50/50 blend of polycarbonate/polyethyleneteraphthalate (XYLEX). Rectangles approximately 60×70 mm were cut fromthe composite structure and were then heated in the thermoformer to 100°C. for 8 minutes. Upon removal from the thermoformer the curvature ofthe rectangles closely approximated the curvature of the mold surfacesand was uniform. This article was then used as an insert for aninjection molded polarized lens.

Although the invention has been described and illustrated with respectto exemplary embodiments thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, without partingfrom the spirit and scope of the present invention. For example,although the present invention has been described above in connectionwith ophthalmic lenses, those skilled in the art that the presentinvention will also be suitable in other optical applications, such asfilters for electronic display devices and enclosures (filters) forlamps, to name just a couple.

1. A method of making a layered lens article, comprising: a) providing a photochromic layer having a minimum degradation temperature; b) providing a substrate that includes a polymer blend and that contains a first polymer having a first glass transition temperature higher than said minimum degradation temperature, said polymer blend having a second glass transition temperature lower than said minimum degradation temperature; c) placing said photochromic layer and said substrate into working relation with one another so as to form a layered composite; and d) thermoforming said layered composite at a temperature below said minimum degradation temperature so as not to degrade the photochromic layer.
 2. A method according to claim 1, wherein the photochromic layer includes at least one photochromic substance selected from the group of substances comprising: naphthopyrans, spironapthopyrans, fulgides, fulgimides, salicylates, triazoles, oxazoles, azobenzenes and silver halide.
 3. A method according to claim 1, wherein step a) includes providing the photochromic layer with outer protective layers prior to thermoforming.
 4. A method according to claim 1, wherein step b) includes forming said polymer blend by blending a second polymer with the first polymer in a predetermined amount that lowers said first glass transition to said second glass transition temperature.
 5. A method according to claim 1, wherein step c) includes bonding said photochromic layer and said substrate with one another so as to form said composite.
 6. A method according to claim 1, wherein step d) includes thermoforming said composite into one of an ophthalmic lens and a pre-contoured ophthalmic lens insert.
 7. A method according to claim 1, further comprising the step of placing a polymer layer into working relation with said composite.
 8. A method according to claim 7, wherein the step of placing a polymer layer includes forming said polymer layer by an injection molding process.
 9. A method of making a layered lens article that includes a substrate and a photochromic layer having a minimum degradation temperature, the method comprising: a) forming the substrate by: (i) providing a first polymer having a first glass transition temperature higher than the minimum degradation temperature; and ii) blending a second polymer with said first polymer to form a blended polymer having a second glass transition temperature lower than said minimum degradation temperature; and b) thermoforming the photochromic layer and the substrate at a temperature lower than said minimum degradation temperature so as to form said layered lens article while avoiding degrading the photochromic layer.
 10. A method according to claim 9, including sandwiching the photochromic layer between two protective layers.
 11. A method according to claim 9, wherein the first polymer includes a carbonate polymer.
 12. A method according to claim 9, wherein the first polymer includes an acrylic polymer.
 13. A layered lens article, comprising: a) a photochromic layer having a minimum degradation temperature; b) a substrate located in working relation with said photochromic layer, said substrate comprising a blend of a first polymer and a second polymer, said first polymer having a first glass transition temperature greater than said minimum degradation temperature, said second polymer selected to cause the blended-polymer substrate to have a second glass transition temperature lower than said minimum degradation temperature so that the photochromic layer and the substrate are thermoformable at a temperature lower than the minimum degradation temperature so as not to degrade the photochromic layer when forming the layered lens article.
 14. An article according to claim 13, wherein said photochromic layer includes at least one photochromic substance selected from the group of substances comprising: naphthopyrans, spironapthopyrans, fulgides, fulgimides, salicylates, triazoles, oxazoles, azobenzenes and silver halide.
 15. An article according to claim 13, wherein said photochromic layer is sandwiched between first and second protective layers.
 16. An article according to claim 13, wherein said photochromic layer and said substrate are operatively configured as an ophthalmic lens.
 17. An article according to claim 13, further comprising an injection molded layer in working relation with said photochromic layer and said substrate.
 18. An article according to claim 17, wherein said injection molded layer is bonded to said substrate opposite said photochromic layer.
 19. An article according to claim 13, further including a thermoplastic polarizing filter arranged adjacent the photochromic layer and/or the substrate.
 20. An article according to claim 13, wherein said first polymer is a polycarbonate and second polymer is other than polycarbonate.
 21. An article according to claim 13, wherein said first polymer is a polycarbonate.
 22. An article according to claim 21, wherein said second polymer is a polyethylene teraphthalate.
 23. An article according to claim 13, wherein said first polymer is a poly(methyl methacrylate).
 24. An article according to claim 23, wherein said second polymer is a butyldyene.
 25. An article according to claim 13, wherein said photochromic layer is sandwiched between cellulose-based protective layers. 